High-strain-rate plastic deformation and fracture behaviour of Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy at room temperature

To study the plastic deformation and fracture behaviour of Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511) alloy under high strain rate loading conditions, a series of dynamic compression tests on Ti-55511 alloy have been performed at constant strain rates ranging from 350 s⁻¹ to 2900 s⁻¹ by means of split Hopkinson pressure bar technique at room temperature. The different strain and strain rate loading conditions are realized by changing the length and velocity of the striker bar, and high intensive localized shear region is induced in Ti-55511 alloy. The dynamic compression stress-strain response, strain rate hardening effect and strain rate sensitivity, and the fracture behaviour are discussed. The experimental results demonstrate that: The strain rate hardening effect and strain rate sensitivity of Ti-55511 alloy are apparent; Brittle shear bands form at high strain rate loading conditions, and the formation of a shear band does not mean the occurrence of phase transformation; Collapse of the specimens occurs along a plane inclined at an angle of about 45° to the compression axis at room temperature for both quasi-static and dynamic compression loading; The shear-compression zone and tension-shear-compression zone coexist in the fracture surface, and collapse of the specimens is attributed to shear failure mechanism for Ti-55511 alloy under compression loading at room temperature.